This invention relates to optical fiber cables and components thereof containing a homogeneous barrier composition suitable to protect optical fibers from hydrogen; it also relates to said homogeneous barrier composition suitable to protect optical fibers from hydrogen.
It is known that hydrogen is detrimental to optical fibers of optical cables and impairs their efficiency. Some compositions able to capture hydrogen before it contacts the optical fibres of optical cables have been therefore proposed. U.S. Pat. No. 4,688,889 teaches to capture hydrogen by means of an hydrogen fixing filler for cables and components thereof containing such filler which comprises:
(a) at least an unsaturated organic silicone having more than 0.2 mmoles of unsaturated groups per 100 g of said compound and having the following general formula: ##STR1## wherein: R and R' are selected from saturated or unsaturated aliphatic radicals and aromatic radicals, PA0 (b) at least a catalyst selected from the group consisting of transition metals, inorganic and organometallic salts of transition metals and organometallic acids of transition metals. PA0 (a) at least a silicon unsaturated organic compound having more than 0.2 mmoles of unsaturated groups per 100 g of said compound and having the following general formula: ##STR2## wherein R and R', which may be the same or different, are alkyl, alkenyl or aryl PA0 (b) at least a catalyst selected from the group comprising inorganic and organic complexes of transition metals and organic salts of transition metals; and PA0 (c) at least an organic solvent substantially non-volatile.
R" and R'" are aliphatic unsaturated radicals, and PA1 n is an integer; and PA1 R" and R'", which may be the same or different, are alkenyl, PA1 and n is an integer; PA1 a vapour pressure of less than 200 Pa at 20.degree. C.; PA1 1 part by volume dissolves at least 0.001 parts by weight of a catalyst of this invention; and PA1 it is mixable with the silicon organic unsaturated compounds of the formula I.
As it is also apparent from the pertinent examples, the catalysts according to said patent are typically in the form of powders, either free or supported onto suitable solid inert materials.
In turn, UK-A-2,172,410 teaches to capture hydrogen with a hydrogen trapping powder which is free or, preferably, supported on a flexible film of paper or polymeric material. As an example of a powder suitable for capturing hydrogen, the said patent mentions palladium on carbon.
Furthermore, it is also known that microbendings substantially reduce optical fibres efficiency (G. Grasso et al. "Microbending effects in single mode optical cables"--International Wire & Cable Symposium Proceedings 1988).
Now, it has been found that the particles of the powders forming the materials of U.S. Pat. No. 4,688,889 and UK-A-2172410 cause microbendings when they are contacted with optical fibres. Said materials are thus less effective than they could be if they were directly contacted with the optical fibres; moreover, also the manufacturing of optical cables is more difficult than it could be if a composition were available, directly applicable in contact with the optical fibres to exert an effective barrier function against hydrogen without causing the drawbacks (microbendings) of known compositions.
On the other hand, it does not appear that any composition was disclosed consisting of a homogeneous phase comprising a silicon unsaturated organic compound of formula I and a hydrogenation catalyst having high hydrogen adsorbing power.